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AUD fall 18 Hearing Science > Last 1/3 Semester > Flashcards

Last 1/3 Semester Flashcards

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1
Q

how movement occurs on the basilar membrane

A

movement increases from base to apex up to the point of maximum displacement, then decreases rapidly as the wave travels up the cochlea a bit further

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2
Q

masking basic definition

A

the process where one signal is made less audible because of another signal that is either present at the same time or close in time

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3
Q

concepts of tone-on-tone masking

A
  • when the probe tone and masker are similar in frequency, the probe tone is masked efficiently
  • when the probe frequency is further away from the masker frequency, there is less masking and often no masking if the probe frequency is lower than the masker (it is difficult to impossible for the masker tone to mask probe frequencies that are lower than the masker frequency because of the physical characteristics of the basilar membrane and traveling wave)
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4
Q

stopped at 10/31

A

start on 11/5 (tone-on-tone)

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5
Q

LPC

A

level per cycle; the intensity present at each individual frequency

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6
Q

equation to find overall level of noise

A

OA=LPC + dB BW
the level per cycle plus the bandwidth expressed as dB
*find dB BW by taking 10log (the bandwidth)

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7
Q

critical bands for auditory filters

A

the range of frequencies most important in masking a pure-tone probe signal
*determine the width of the CB by finding the narrowest band that just masks the probe
*in general CB is about 1/4-1/3 octave
(wider in high frequencies and narrower in low)

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8
Q

is masking a probe with a narrow band of noise a linear function?

A

yes, if the probe is increased 10dB you can mask it by adding 10dB more to the masker

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9
Q

bandwidth of NBN used clinically

A

1/3-1/2 octave wide

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10
Q

number of critical band in the human ear

A

24-25

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11
Q

another name for critical band

A

bark

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12
Q

sizes of critical bands

A

vary in size with frequency; are roughly equal below 1000Hz, but then increase above 1000Hz

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13
Q

equivalent rectangular bandwidths (ERB)

A

frequencies in a NBN closest to the probe frequency are most effective for masking; not all frequencies are important for masking a tone; (frequencies within a CB are close enough in frequency to mask each other; masking a higher frequency sound takes a wider range of frequencies)

  • rectangle superimposed on figure gives a convinient way to describe the limits of a filter
  • the area under the rectangle is the same as the area under the curved auditory filter
  • as intensity increases, the ERB widens (more frequencies important in masking)
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14
Q

relationship between critical bands and loudness

A

if tones are in different CBs and are presented together, more neurons will fire (because neurons from both CBs) and the sound will seem louder
**4 tones within one CB will seem softer than 3 tones in 1 CB and 1 in another

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15
Q

why are acoustic reflexes lower for BBN than pure tones?

A

BBN is perceived louder because it activated many CBs (used in SPAR testing to predict sensitivity)

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16
Q

remote masking

A

high frequency sounds masking low frequencies; not really allowed by basilar membrane, however there is a small amount of this kind of masking

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17
Q

possible explanations for remote masking

A
  • acoustic reflex= high frequencies trigger the reflex which stiffens the chain inhibiting low frequency transmission
  • efferent system= path of neurons inhibits function of cochlea and efferent system suppresses cochlear amplifier, helps w/ speech in presence of noise
  • distortions= create even lower tone to mask the low tone (F2-F1)
  • **masking is more than just result of waves on the basilar membrane, the CNS and OHCs are also involved
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18
Q

psychophysical tuning curves (PTCs)

A

a probe tone is presented
a narrow band masker is presented
as the narrow band masker gets further away it takes higher intensity to mask the tone
this correlates to the traveling wave theory

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19
Q

tuning curves for low vs high frequencies

A

curves for lower frequencies are wider than those for high frequencies because of the octave scale (non-linear) if they were on a linear scale it would make them all look similar (high frequencies are collapsed due to the scale)

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20
Q

Q10

A

a measure of sharpness (q= quality factor) gives you an idea of how good cochlea is doing with certain frequencies

  • find the point of the tip of the tuning curve, and go up 10dB
  • draw a horizontal line at this intensity, and find the frequencies that intersect the line
  • —-take the point at 10 minus the other point at 10 and divide the frequency of the pure tone by this range
  • the probe tone frequency divided by the range of frequencies that Q10 line intersected gives you the Q10 of the psychophysical tuning curve
  • ***Q10 addresses the difference on the x-axis, Q10 gives ratio to compare
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21
Q

Q10 examples and values

A

ideally we want Q10 to be around 10 and not too wide (smaller than 3 and shows cochlear problem)
*normal range is 3-10
above 10 is narrow which just shows good discrimination
*higher frequencies are more narrow than low?

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22
Q

TEN test

A

threshold equalizing noise test (Moore)
(HL)= phones
(ER3)= inserts
broadband signal with a spectrum shaped so that it will elevate thresholds of normal hearers to the same level at all frequencies

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23
Q

TEN procedure

A
  • hearing loss< or = 60dB HL, TEN is presented at 70dB HL
  • loss > or = 65dB HL, TEN is presented at 10dB above threshold
  • *if ten is uncomfortable loud or threshold is at 90dB HL (max for ten) then set it to the audiometric threshold
  • if threshold is above 90 dB HL, can’t test
  • present masker and find threshold using 2 dB steps
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24
Q

criteria for dead region with TEN test

A

1) a shift > or = to 10 dB from original threshold
AND
2) a shift > or = to 10dB above masking level
***indicates cochlear dead region
**if change is 5dB above noise, increase noise and repeat
**not used very much in US (helps to not amplify areas that can’t use it)

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25
Q

temporal integration

A

how the auditory system takes advantage of longer duration signals
*above 200-250msec is infinitely long

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26
Q

temporal processing and pitch perception

A
  • a 3000Hz tone can be differentiated from a 3009Hz tone
  • 1 microsecond change in period is what we can perceive
  • tonality perception= perceive as pure tones if they are long enough, but as a click if they are short because limits of the transducer not allowing the intensity to have the gradual rise and fall it needs to get to the maximum without distortion, going to maximum without rise time will result in distortions creating a Broadband signal and doesnt have enough cycles to detect as a pure tone
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27
Q

gap types and definitions

A
  • within channel= with pure tones; signal before and after pause is the same
  • between channel= white noise; signal before pause is different than after
  • ***these pauses can be really really short
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28
Q

gap detection and frequency

A

can detect smaller gaps for high vs low frequncy

  • reason for this relates to auditory filters; the narrower the filter, the longer it vibrates
  • *high frequencies has wider filters than low
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29
Q

gaps in white noise

A

behave like high frequency sounds

*2 msec gaps can be detected if the noise contains energy up to 12kHz

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30
Q

minimum starting time between 2 clicks we can detect

A

1-2msec

  • yet we can’t tell which came first, need 20 msec to do that
  • detection of gaps and which signal arrives first is important for speech processing and relates to distinguishing voiced from unvoiced consonants
  • *abnormal timing detection can relate to speech perception problems
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31
Q

temporal modulation transfer functions

A
  • the amplitudes of signals are modulated at different rates
  • -if the rate is very slow, we will be able to detect small modulation changes
  • -the faster the rate of modulation, needs larger modulation to detect
  • –in case of modulations above 1000x/sec (1/milisecond), the amplitude fluctuation is not noted at all
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32
Q

name the two types of temporal masking

A

forward masking

backward masking

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33
Q

forward masking

A

present noise, turn it off, then present tone

  • using a click as stimulus and white noise as a masker at a constant level
  • -a delay of 1msec can have up to 40dB of threshold elevation
  • -with 50 msec of separation, the masking effect is down to 10dB
  • -by 200-250msec, there is no effect
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34
Q

physiologic explanation of forward masking

A
  • basilar membrane continues to vibrate making it harder to encode a low-intensity sound that follows
  • the refractory period
  • the efferent system may also play a role
  • -pathway of neurons that go from brainstem to inner ear, controls the active mechanism of the cochlea
  • ****tuning curves are sharper in forward masking paradigms
35
Q

backward masking (and explanation)

A

present tone, turn off, present noise

  • may simply be confusion by the listener as to the task, rather than a physiologic phenomenon
  • *training can reduce effect
  • only occurs if the gap is less than 20 msec
  • the size of the effect can be up to 40dB if the inter-stimulus interval is very shor
  • if the following noise is much louder than the probe, it will make neurons release more neurotransmitters, causing the following neurons to fire faster and override the probe
36
Q

diotic

A

same (identical) stimulus presented to both ears at the same time

37
Q

dichotic

A

different stimuli presented simultaneously to each ear

38
Q

monotic

A

stimulus presented to only one ear

39
Q

lateralization

A

perception of sound location in the head (under headphones)

40
Q

spatial hearing

A

the cues that we use to localize sound sources, and the neural mechanisms involved in processing this info

41
Q

localization

A

perception of sound location in space

42
Q

binaural summation

A

when a sound is presented diotically, there is a summation of the acoustic energy
*on average: 2-3dB

43
Q

monaural vs. binaural loudness perception

A

monaural signal must be increased 3-6dB to sound equally loud as the signal binaurally

  • binaural difference limen for intensity are about 1/2 the size of monaural difference limens
  • *DL frequency is improved too
44
Q

binaural beats

A

similar concept to aural beats

  • 1000Hz in one ear and 1005Hz in other will be perceived in terms of beats as it would with both in 1 ear
  • 1000 and 1004Hz= listener hears 1002 Hz beating 4x/second
45
Q

central masking

A
  • noise put into one ear elevates the threshold of the other ear roughly 5 dB
  • as far as we know, it is something that happens at the brainstem level
  • not linear (1:1) increase of masker won’t add more than the 5dB
46
Q

binaural fusion

A

2 sounds- 1 image

  • for CAP test, high frequency of word and low frequency of same word presented to separate ears and brainstem puts together so you hear the whole word
  • **also happens when listening to music with headphones
47
Q

binaural squelch

A

central nervous system focuses on the ear with better signal to noise ratio (SNR)

48
Q

azimuth

A

the angle where the sound arrives from, compared to where the subject is

  • o degrees is directly in front
  • 90 degrees is to the right
  • 180 degrees is directly behind
  • 270 degrees is to the left
49
Q

factors to localization

A

azimuth
temporal cues
intensity differences
combined intensity and phase differences

50
Q

temporal cues

A

1) the time of arrival

2) phase differences at both ears

51
Q

the time of sound arrival as a temporal cue

A
  • speed of sound is not affected by intensity or frequency
  • midline ( 0 azimuth or 180 azimuth) then the signal arrives to both sides at the same time
  • a sound arriving from 90 azimuth travels the distance between ears in about 0.66msec
  • -45 degree azimuth= 0.36 difference in time of arrival
  • -30 azimuth=0.25 msec
52
Q

phase differences at both ears as temporal cue

A
  • phase angle arriving at each ear ( specifically for low frequency helps w/ localization)
  • low vs high frequencies=higher chance for phase angle arriving at both ears to be similar for high than with low
  • -1) find period
  • -2) find difference in arrival time
  • -3) find ratio between the 2
  • -4) multiply by 360 degrees to find the angle of the ratio between the 2
  • *intensity differences
  • head shadow effect
  • —-low frequencies wrap around head so not affected, but high frequencies are affected because signal is reflected by the head
  • —-can attenuate up to 10-20 dB
  • —-sounds from behind and pinna
  • —-0 and 180 azimuth use the shadow effect of the pinna to decide where sound is coming from
53
Q

combines intensity and phase differences (temporal cues and frequencies)

A
  • low frequency=phase
  • high frequency=intensity
  • -ability to localize is worst at about 3000Hz
  • minimum audible angle: the smallest change detectable
  • -localization error-when angle change is too small to detect
  • -average of 10 degrees to detect
  • -3000Hz need 25 to detect ( 25 degree localization error)
54
Q

where is the first place for auditory info from both sides

A

SOC, majority of neurons decussate to the contra side at the SOC level
*soc receives both ipsi and contra input

55
Q

cell types of the soc

A

1st letter is for the contra effect

  • EI= contra excitatory and ipsi inhibitory
  • IE
  • EE
  • EO= contra excitatroy, ipsi no affect
56
Q

interaural time difference and lateralization

A

the sound begins to move from midline toward the “leading” ear

  • 10 microsecond difference is all you need to tell a difference
  • =660 microsecond difference is where the sound is audible just in the leading ear though it is present in both
57
Q

interaural intensity difference and lateralization

A
  • 1dB can tell difference (closer to louder side)
  • 10dB difference is where you only hear the sound in one ear
  • ***this is the concept for the stenger test
58
Q

masking level difference

A

the ability to hear better in the presence of noise

  • binaural release from masking
  • **sumbols:
  • m=stimulus is monaural
  • o= stimulus is binaural in phase
  • pi= stimulus is binaural out of phase
  • t=time delayed
59
Q

what conditions give the best results of release from masking

A

SpiNo condition (stimulus is binaural out of phase and noise is binaural in phase)

60
Q

release from masking

A

must have symmetrical hearing for release from masking

  • smaller than normal masking level difference suggests retrocochlear pathology at the brainstem level
  • done on low frequencies a (250 and 500) and spondee words
  • if there is a little delay in the presence of noise, it can result in an improvement of perception from 3-10dB
61
Q

articulation index (french and steinberg, 1947)

A

how well you hear speech

  • 0-100%
  • mueller and killion make count the dots which is trying to simplify the articulatio index
  • *it is mor important to understand consonant sounds than vowel sounds
  • —emphasis on higher frequencies
  • —-# of dots in the audible range and that gives you your %
62
Q

why can two pts with the same audio perform differently on speech tests

A

Because it is just s prediction and other factors can play a role such as age (younger will do better) and IQ (can they fill in blanks and figure out words)

63
Q

CHL vs SHL and hearing aids

A

A major issue with CHL is loudness so just need loudness boost to understand speech, SHL issue can be processing and need programming of hearing aids to improve speech understanding (not flat gain across all frequencies)

64
Q

Cochlear loss and growth of loudness

A

Recruitment= abnormal rapid growth of loudness

*dynamic range for SNHL (specifically cochlear) is much smaller than that for normal hearing individuals

65
Q

Recruitment theories

A

Spread to other outer hair cells

Active mechanism of the cochlea

66
Q

Spread to outer hair cells theory of recruitment

A

Kiang et al 1970

*where their is hearing loss on the basilar membrane, you recruit more and more hair cells to fire

67
Q

Active mechanism of the cochlea theories of recruitment

A

Loss of outer hair cells, and functioning Inner hair cells Moore et al

  • tested subjects with unilateral HL; matched loudness between ears, then presented BBN which is notched at the frequency matched; this masks entire basilar membrane with exception of the area they want to test
  • **recruitment still happened disproving kiang
  • ***ohcs amplify signal at softer levels, so when this is lost there is no active mechanism so no gradual growth from ohcs
68
Q

Basilar membrane velocity theory of recruitment

A

Measured the vibration of the basilar membrane at 9000 and 1000hz and injected chinchilla with ototoxic drugs then measured speed

  • time in minutes after injection
  • 70 dB or higher was enough for basilar membrane to not need OHC amplification
  • need OHC for softer levels until the point where The signal is loud enough
  • in agreement with Moore
69
Q

Difference limens for intensity and

OHC function

A

Hearing impaired people have better sensitivity for detecting changes in intensity

  • 10 dB SL for 0db HL threshold can’t detect as small of change as 60db HL threshold
  • 1 dB change for 80 dB HL for thresholds at 0db HL and 60 dB HL, then both subjects will do the same because stimulating the inner hair cells directly
70
Q

Threshold integration and hearing loss

A

Normal hearing vs hearing loss

  • duration and threshold
  • example 20-200msec increase in duration
  • -normal hearing: 15db with 20msec and 5db with 200msec
  • -hearing impaired: 73 dB with 20msec and 70db with 200msec
71
Q

Wide critical bands

A

Happens with hearing loss

  • this is why background noise becomes such an issue
  • what does this mean?
  • loss of ability to distinguish frequencies
  • larger area able to do masking because less finely tuned curve as opposed to small range of frequencies able to affect one frequency
  • low frequencies and amplification-you don’t want to amplify lows a lot because with wider CB and amplified lows you make it easier for noise to mask the signal for the patient
72
Q

Cochlear dead regions

A

No ohcs or inner hair cells, neural fibers here die, doesn’t matter how loud you stimulate there won’t be a response

  • use off frequency listening
  • dead regions aren’t always with severe to profound thresholds (they can be between 50-80) due to how loud you need sound to stimulate neighboring regions
73
Q

Off frequency listening

A

Occurs when there are cochlear dead regions

  • traveling wave is large enough to stimulate neighboring regions, so pt detects signal, but not via the dead region
  • most seen with steeply sloping audio gram because neighboring regions have better thresholds for off-frequency listening (35db per octave slope or more)
74
Q

What is perceived with off frequency listening?

A

When neurons are not tuned to tone, pt will perceive more of a staticky sound than a tone

  • noise, static, distorted
    • pt reports pure or clean tone when no dead region
75
Q

Psychophysical tuning curve

A

What is the best narrow band noise to mask a probe tone

*masker is low frequency to mask high frequency amplitudes as expected in normal cochlea

76
Q

Psychophysical tuning curves for cochlear dead regions

A

The higher frequency is able to mask probe a lot better for low frequency dead region

  • for high frequency dead region a lower masker is much better able to mask toke
  • ***shows different area than actual probe is being stimulated to hear probe
77
Q

Amplification for those with dead regions

A

Can’t amplify dead regions

78
Q

Frequency shifting

A

Send amplification to non-dead zone (frequency is compressed and sent to neighboring region)

79
Q

What technology can be used for dead regions

A

Hearing aids and cochlear implants

*hybrid implants for ski sloping loss=electrode just on basal portion of the cochlea

80
Q

Gap detection thresholds for high vs low tones

A

Easier to detect gaps in high frequency signal vs low frequency signal
*2 mused for high, longer for low

81
Q

Gap detection for white noise

A

Relies on high frequency signal in the noise to detect gaps

  • if high frequency loss, gap detection becomes poorer
  • *normal hearers have improved gap detection ability as the sound levels increase to about 60 dB SPL
  • *at high intensity (90db) normal and hearing impaired behave more alike
    • poor gap detection can impact speech: /d/ vs /t/
82
Q

Temporal modulation detection ability

A

A 10hz modulation means 10 changes per second

  • a smaller change can be detected by hearing impaired due to recruitment
  • hearing impaired subjects have difficulty detecting fast modulations
83
Q

Pitch perception ability

A

Poorer pitch perception abilities with hearing loss

  • frequency difference limen is worse with cochlear hearing loss
  • the difference between hearing impaired and normal hearing difference limens is greatest at high frequencies and more similar at low frequencies due to widening critical bands
84
Q

Laurel vs yanny

A

Transducer plays role
Hearing loss plays role
Auditory processing
Priming (do they know what they are listening for?)

AUD fall 18 Hearing Science (3 decks)

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